Considering pea plants like the ones Mendel studied, you will be crossing plants
ID: 67809 • Letter: C
Question
Considering pea plants like the ones Mendel studied, you will be crossing plants based on two traits: seed pod color and seed shape. Seed pod color: yellow seed pods are dominant and green seed pods are recessive. Seed shape: round seeds are dominant and wrinkled seeds are recessive. If a homozygous yellow, heterozygous round seed parent is crossed with a green, heterozygous round seed parent, what would be the predicted phenotypic ratio, of their offspring? Define the letters for each trait, set up the problem, complete the Punnett Square, and indicate your answer, showing all of your work.Explanation / Answer
Trait - Yellow seeds – Y allele
Trait - Green seeds – y allele
Trait - Round seed shape – R allele
Trait - Wrinkled seed shape – r allele
The dihybrid cross in the problem is,
Homozygous yellow and heterozygous round seeds X green and heterozygous round seeds
YYRr X yyRr
Gametes of first parent are YR, Yr, YR and Yr.
Gametes of the second parent are yR, yr, yR and yr.
Punnett Square
YR
Yr
YR
Yr
yR
YyRR
YyRr
YyRR
YyRr
yr
YyRr
Yyrr
YyRr
Yyrr
yR
YyRR
YyRr
YyRR
YyRr
yr
YyRr
Yyrr
YyRr
Yyrr
Number of offspring types
Genotypes
Seed Traits
1
YyRR
Yellow Round
2
YyRr
Yellow Round
3
YyRR
Yellow Round
4
YyRr
Yellow Round
5
YyRr
Yellow Round
6
Yyrr
Yellow Wrinkled
7
YyRr
Yellow Round
8
Yyrr
Yellow Wrinkled
9
YyRR
Yellow Round
10
YyRr
Yellow Round
11
YyRR
Yellow Round
12
YyRr
Yellow Round
13
YyRr
Yellow Round
14
Yyrr
Yellow Wrinkled
15
YyRr
Yellow Round
16
Yyrr
Yellow Wrinkled
The phenotypic ratio is 12:4 for Yellow Round and Yellow Wrinkled seeds.
YR
Yr
YR
Yr
yR
YyRR
YyRr
YyRR
YyRr
yr
YyRr
Yyrr
YyRr
Yyrr
yR
YyRR
YyRr
YyRR
YyRr
yr
YyRr
Yyrr
YyRr
Yyrr